Since FromZeroes and FromBytes ban UnsafeCells, and since rust-lang/unsafe-code-guidelines#455 implies that there's no way to "disable" interior mutability, our impls of FromZeroes and FromBytes for MaybeUninit<T> with no bounds on T are unsound. See also this discussion.

One option we may want to consider is introducing a NoCell trait that is a super-trait of all of our traits (other than Unaligned) so that we can do e.g. impl<T: NoCell> FromBytes for MaybeUninit<T>.

A note on semver: When releasing this, it's doubtful that anyone is relying on this behavior. We may want to just release 0.7.X (whatever the next patch version is at the time of releasing) and yank the previous 0.7.Y versions.